Erika Wennerstrom’s candid lyrics and no-frills songwriting would not seem to imply a flighty, focus-challenged artist.

As lead singer of the Austin, Texas, quartet Heartless Bastards, the 34-year-old Ohio native peddles a sort of rootsy garage rock that recalls — and is frequently compared to — fellow Ohioans the Black Keys, whose Patrick Carney helped give the Bastards their first big break.

But to hear Wennerstrom tell it, her band’s progress is often the miraculous result of being able to write anything without distraction.

“I don’t know if ADD’s the right phrase, but I just tend to have a hard time focusing,” Wennerstrom said via phone from her tour van in Texas. “Or if I sit down and try to work on a song and I get a little bit of writer’s block, I end up calling a friend and saying, ‘Hey, you wanna go to lunch?'”

Despite that, Wennerstrom has managed to release four well-received full-lengths since 2005, including this year’s “Arrow,” which moves the Bastards’ sound forward with accessible songwriting and slick, punchy production from Spoon drummer Jim Eno, a fellow Austinite.

Still, Wennerstrom is a musical idealist. Her commitment to playing in a band and expressing herself through melody and chords practically oozes from each track of “Arrow.”

“I’m writing a lot of things that are personal to me, so it takes me a while to figure out how to express that — and maybe even feel comfortable putting that out for the world to hear,” said Wennerstrom, who brings her band to Boulder’s Fox Theatre on Wednesday, Oct. 17.

Anyone who has seen the Bastards play in recent years has witnessed a more ferocious version of Wennerstrom’s formerly tentative stage presence. She’s still more intent on hitting every soulful note than engaging in canned banter or choreography, but her purposeful playing has lately felt effortless.

“I think past (band members) were all pretty shy as far as performing, and I feel like the band I’m playing with now is a lot more confident, stage-wise,” said Wennerstrom, who reunited with bassist Jesse Ebaugh and drummer Dave Colvin from her raw early demos, as well as adding guitarist Mark Nathan. “Plus the fact that I’ve been doing it for nine years at this point.”

When Wennerstrom first cut those demos for songs such as “Autonomy” and “New Resolution” in 2002, she wasn’t thinking about where her band would be a decade later — or if it would even exist at all. But having toured extensively and become a critical and summer festival favorite, Wennerstrom is grateful that the Black Keys’ Carney sung the Bastards’ praises all those years ago, leading to her first record deal with Fat Possum.

“I guess if we could fill arenas five years from now (like the Black Keys) that would be a pretty neat feeling, but at the same time I feel proud of where we’re at,” she said. “With the current lineup it really does feel like we’ve come full circle.”

Wennerstrom’s also branching into film with her songs for the indie flick “Winter in the Blood,” based on the novel by James Welch. Most of the soundtrack was produced by the Bastards on an old ranch in Marfa, Texas, with Decemberists’ multi-instrumentalist Chris Funk, but it will also include contributions from Robert Plant and Cass McCombs.

“They hadn’t filmed the movie yet and wanted everything to happen organically, so I read the book and the script and wrote this song based on that without ever seeing the footage,” Wennerstrom said. “I was a little bit nervous they weren’t going to find that it fit the film, but it worked out really well and I’m proud of it.”

Wennerstrom said she would do it again, but with one request.

“This approach was unique and worked out well, but I would actually love sometime to see footage and be inspired by the imagery.”

In spite of her self-professed writer’s block, Wennerstrom’s career has lately hinted that she won’t have to look far for another chance.

John Wenzel is an A&E reporter and critic for The Denver Post who writes regularly about music, comedy, film, books, video games and other popular culture. Over the years he has also contributed to Rolling Stone, Esquire, The Guardian, Vice, Splitsider and a few others.